Want to Generate Energy? Go Fly a Kite

More than 200 years ago, Benjamin Franklin advanced the research of electricity by flying a kite. Now, a German company is taking a slightly different tack on that old idea by using kites to generate energy.

Nature Technology Systems (NTS) GbH has designed a principle based on the same elements of energy output, speed, and consistency used in wind turbines, according to the company. The result is a method that uses clusters of kites to form an aerial power station 1,000 feet to 2,000 feet in the air that produces energy on the ground.

The system, which NTS is testing in collaboration with the Fraunhofer Institute for Manufacturing Engineering and Automation IPA in Stuttgart, works like this:
The kites fly at high altitudes, where there are strong winds, on a tether of cables about 2,000 feet in length that's connected to vehicles on the ground, said Joachim Montnacher, an engineer at the IPA, in a press release. Those vehicles are pulled around a circuit on rails, producing kinetic energy that is then turned into electricity by a generator. The vehicles include the control and measuring mechanisms for the energy generated.

One of the test kites being used to create energy according to a method designed by Nature Technology Systems in Germany makes its first flight. The company -- which partnered with Fraunhofer Institute for Manufacturing Engineering -- said the system it created uses the same principles as wind turbines but is more efficient and environmentally friendly. (Source: Fraunhofer Institute for Manufacturing Engineering and Automation IPA)

Specifically, the kites generate the energy through buoyancy achieved when a kite flies in high wind speed, according to NTS. Anyone who has ever flown a kite will know that the pull of the kite increases the faster the kite flies. NTS's design of the system allows the kite to surpass a buoyancy of about 110 lb/22 ft. "So when we fly a 20m2 (215 ft) sized kite it will be able to drag and lift up to 1 ton in weight," the company explained on its Website.

NTS insists its kite energy farms are more efficient, economical, and environmentally friendly than wind turbines. Because typical wind turbine rotors max out at a height of about 650 feet, they can't take advantage of winds at higher elevations, which are stronger. "Depending on wind conditions, eight kites with a combined surface area of up to 300 square meters (about 3,200 feet) can equate to 20 conventional 1 megawatt wind turbines, Montnacher said.

The kites also avoid material and financial investment in wind turbine infrastructure, which has more of an impact on the environment.

NTS will continue to test its kite system and will reveal its findings and seek feedback from the energy industry once these tests are complete, the company said.

The Germans aren't the only ones taking to the skies to find new and different ways to use wind and air currents to create alternative sources of energy. The US military recently tested a method to fly aircraft in formation that would promote fuel efficiency by using vortex surfing, a technique similar to what bicycle racers and migrating birds do when they cluster together to draft off each other.

Thanks for your comment, bobjengr. I hear what you're saying and think there are a lot of issues with this idea to be solved before it would actually be viable. But if anyone can come up with answers, the Germans can! They are doing remarkable things in wind energy. I guess time will tell.

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I always have difficulty with what is and is not practical. Years ago, I thought airbags were the most illogical devices known to man and yet today, they save countless lives each year. This approach to harvesting the wind is definitely unique but as others have mentioned, the concept seems to be laden with complexities that would make the application very unreliable. Obviously a complement to existing power sources, I would imagine a "hit-or-miss" situation at best. Very interesting though and thanks Elizabeth for writing about this one.

While the Benjamin Franklin kite story is known to just about everyone who went to elementary school in the U.S., it's almost certainly untrue. Franklin wrote an article suggesting a version of the experiment, but he didn't claim to have actually performed it himself -- and if he had done it the way it is usually described, it's unlikely that he would have survived.

That being said, I teach a U.S. citizenship class, and always mention the kite story to my students (along with the story about George Washington and the cherry tree, which is also probably a legend). First, because it's a story that most people who grew up in the U.S. know, and is a part of our popular culture. Second, because Franklin's scientific fame helps explain why he was chosen to be the U.S. diplomat to France during the Revolutionary War, which is what USCIS thinks you ought to know about him.

"the faster a kite flies the harder it pulls". Meh. Last I checked, kites were pretty much stationary in the sky and the wind moved past them. This statement makes no sense.

Yes, if you pull in the kite it will pull harder because you are increasing the relative wind speed the kite sees. But a kite is basically a stationary device that provides lift when air moves past it.

It strikes me as they are chasing an awkward way of achieving power with railway tracks and the like.

A far simpler way would be to build the kite so you could dynamically play with the lift and drag, and operate the kite in "cycles". You would set up your kite cable winches to be able to spool the cable in and out, and any necessary braking on the winch drum(s) would be converted to useful energy.

The first part of a cycle would be with the kite flying high, at the desired high altitude, (read: higher wind speeds) but pulled as close in to the winch point as possible. Now, change the kite characteristics to get maximum drag while just maintaining the desired altitude. Begin letting out cable and harvest the energy from the pull of the kite. Depending on the airspace you are allowed to operate your kite in, this may be many thousands of feet downrange.

Once the kite has reached the far end of the cycle, you need to bring it back to the starting point. Presumably, from the data the company has provided, there are lower wind speeds at lower altitudes. Therefore you pilot the kite, again by playing with lift and drag on the kite, to minimize the drag and allow just enough lift to bring it back upwind with your winches, presumably expending less energy than your gained by the wind towing the kite downwind.

The version of the kite-type system that I saw that made more sense put the turbines up in the kite. The generators could be run as motors to fly up into the wind area, thgen revert to generating power from the high altitude wind. The major problem with this approach was the transmission of the power back to the ground. My suggestion is to use quite high voltage and separate cables for each phase. Then you could have a twenty kilovolt transmission line with fifty feet of separation. It really is an interesting concept, and less complex than flying a kite in circles. I was never able to do that in a sailboat, so why should it be any easier with a kite.

No, mrmikel, most General Aviation flights are still Visual Flight Rules. Commercial Aviation typically flies Instrument Flight Rules and at altitudes that wouldn't cause any problems to this system, but small planes would have real issues.

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